A plate cylinder supports a printing plate in a printing unit. The plate cylinder is supported in the printing unit to rotate about its axis. The printing plate has a surface which defines the image to be printed. Ink is applied to the printing plate on the plate cylinder, and the inked image is printed on paper or other material when the cylinder rotates.
The printing plate is formed as a thin sheet of metal, and is mounted on the plate cylinder by wrapping the sheet around the cylindrical outer surface of the cylinder. When the plate is thus mounted on the cylinder, opposite edges of the plate extend along the length of the cylinder. A locking mechanism within the cylinder engages the opposite edges of the plate to hold the plate on the cylinder when the cylinder rotates.